1. Field of the Invention
The present invention relates to a process for preparing chlorinated carbonyl compounds with improved selectivity and improved conversion in jet loop reactors, wherein the corresponding unchlorinated or partly chlorinated carbonyl compounds are reacted with chlorine in a continuous or semicontinuous mode.
2. Background Art
Chlorinated carbonyl compounds are building blocks for numerous products in synthetic organic chemistry for applications, for example, in the pharmaceutical and agrochemical industry.
The literature describes various methods of chlorinating carbonyl compounds. The chlorination is performed in a stirred tank, tubular reactor, a combination of tubular reactor and stirred tank, or in a bubble column. The insufficient mixing in the individual reactor types often results, locally, in an inhomogeneous chlorine concentration and in temperature inhomogeneities within the reactor, which give rise to a broad spectrum of by-products. This results in an inadequate selectivity and an inadequate conversion based on the target product.
The individual reactor types known from the prior art have substantially been optimized with regard to their mixing performance. In addition to the use of sparging stirrers in stirred tanks and static mixers in tubular reactors, a wide variety of different gas distributors are used in bubble columns, or complicated chlorinations are performed in the gas phase. The heat is removed by internal heat exchangers and optionally by external heat exchangers.
In the chlorination of carbonyl compounds, the conversions are often incomplete; selectivities and hence yields are often low. The subsequent workup, which is necessary as a result, is technically complicated, gives rise to residual substances and makes the production more expensive as a result. In addition, the chlorinated and partly chlorinated carbonyl compounds are often thermally unstable and tend to thermal decomposition.
In order to enhance the selectivities and the conversions in the chlorination reaction, the prior art has proposed various processes. EP 0234503 describes, for example, the addition of catalysts to the reaction mixture. When catalysts are used, the purity of the unchlorinated or partly chlorinated carbonyl compounds, which is relevant for high catalyst activity, is often achievable only by additional workup steps, and the high catalyst cost is reflected in the preparation costs.
GB 2036016 describes the performance of the chlorination in the gas phase. These processes are technically very complicated, since some of them require high reaction temperatures at the start for the chlorination in the gas phase, and only a low space-time yield is achieved as a result of the gas phase reaction. Multistage workup processes are likewise needed for the reactants and products, which in turn entails yield losses.
DE 19842332 discloses a jet loop reactor and a process and apparatus for biologically purifying wastewater. There is no indication that such an apparatus could be used for chlorinating compounds.